Electrophotographic developing device



March 18, 1958 R. w. GUNDLACHI ELECTROPHOTOGRAPHIC DEVELOPING DEVICE Filed Dec. 21, 19 54 MMVR. Y. M w 0K m w R W M m. GI T i W A n Y M K 0 R w United rates Patent ELEcTnorHoroonArmc nitvELoPlNG DEVICE Robert W. Gnndiaeh, Spencer-port, N. Y., assignor to The Haloid Company, Rochester, N. Y., a corporation of New York Application December 21, 1954, Serial No. 476,711

1 Claim. (Cl. 118-309) This invention relates to an electrophotographic developing device.

Electrophotographs are made by exposing the electrically charged photoconductive surface of the electro photographic plate so that it acquires a latent image which is then developed by flowing oppositely electrically charged electrophotographic developing powder over the image side of the plate. The powder adheres inversely substantially in proportion to the degree of exposure to the light so as to produce a positive powder image. Each time the developer is flowed across the plate it is called a pass and two passes are usually necessary.

Prior art devices have comprised a box-like arrangement having an opening forming a frame which is closed by placing the exposed electrophotographic plate over this opening with its image side facing the inside of the box. With the developing powder previously placed in the box, the box is inverted and rocked back and forth to effect the two passes. Initially the image side of the plate is facing downwardly because the box must be arranged with its opening facing upwardly when the plate is positioned. As the box is rotated in either direction so as to first bring the plate to a vertical position the developing powder simply slides to one end of the box without contacting the plate. Continued rotation causes the plates image side to face upwardly and by rocking the box the powder slides over the plate successively in opposite directions.

In certain types of electrophotographic processing this heretofore necessarily reciprocative action, or rocking back and forth, is undesirable. For example, developing uniformity by unskilled persons would be simplified if the box could be provided with a suitable means for turning it continuously in one direction through one complete turn at a uniform speed. With the prior art developing devices such a procedure provides but a single pass instead of the preferred two passes.

With the foregoing in mind, the principal object ofthe invention is to provide an electrophotographic developing device providing for the desired two passes simply by rotating the device continuously in one direction whereby to eliminate the need for any kind of reciprocating action. In attaining this object it is desired to maintain the device as simple as possible both to keep down its manufacturing cost and, of equal importance, to avoid complications in connection with the operation and servicing of the device.

A preferred form of the invention is shown in the accompanying drawings, in which:

Fig. l is a vertical cross-section of an electrophotographic developing apparatus equipped with the invention;

Figs. 2 and 3 are sectional views taken along the lines 22 and 3-3, respectively, of Fig. l; and

Figs. 4A through 4H, inclusive, are a series of sequential operational views showing the relation of the developing apparatus, the developing powder, and the electrophotographic plate at 45 intervals of rotation during a cycle of operation.

As shown in the drawings, the electrophotographic developing apparatus follows the prior art construction insofar as it comprises a relatively shallow rectangular box having a top wall 1 through which an opening 2 is formed to define a frame. Usually the electrophotographic plate is rectangular and the opening 2 follows this contour so as to form a rectangular frame, the edge of the opening being bounded by a deformable seal 3 made of material such as rubber, or the like. Side walls 4 depend from the top wall 1 and with the latter define opposite side portions for the described frame. These side walls 4 are provided with trunnions 4a that are pivotally mounted in journal bearings 5 supported by upstanding brackets 6 which are sufficiently high to permit the device to rotate about an axis, provided by the bearings 5, which extends transversely with respect to the frames side portions.

As shown by the drawings, the top wall 1 extends in opposite directions beyond both of the end portions of the frame outlined by the rubber seal 3, end walls 7 and a bottom wall 8 together with the side Walls 4 completing the box-like contour of the device. Since the top wall 1 extends in opposite directions from the frame and because the side walls 4 and the bottom wall 8 are coextensive therewith, the wall portions beneath the extending top wall portions enclose a space extending beyond both end portions of the frame and thereby define developing powder container portions having interfacing mouth portions respectively indicated at 9 and 16.

Customarily an eleotrophotographic plate is carried in a frame or cassette. Thus, the electrophotographic plate 11, having a photoconductive surface 11a, is shown as being mounted within a frame 12 which may include a groove 13 for a dark slide. The plate 11 is illustrated as being pressed tightly against the seal 3 by releasable fastening means 14 which serve to maintain a dust-tight seal between the plate 11 and the developing device. It is to be understood that the plate 11 is exposed in other equipment and is positioned on and fastened to the illustrated device, the dark slide being removed and the connection with the device made under conditions shielding the plate from all light of sufficient intensity to affect the latent image resulting fromv the exposure. Any suitable detent device (not shown) may be employed to maintain the developing apparatus in a substantially horizontal position, as shown in Fig. 1, while electrophotographic plate 11 is being secured to or removed from the apparatus.

It can be seen that, as so far described, rotation of the box-like device would permit developing powder inside of the box to slide along the top of the bottom wall 8 until there is sufiicient rotation to cause the plate 11 to face upwardly, that from then on, with continuous rotation, the powder would slide over the plate 11 once which would then complete a full turn or rotation through 360 without providing the desired second pass.

According to the present invention a transverse bailie plate 15 is located within the mouth portion 9. This plate 15 is rigidly positioned and it extends from the bottom wall 8 upwardly until adjacent the top wall 1. This plate 15 has its ends connected with the walls 4. The only space between the edges of the plate 15 and the inside of the device is that between the upper edge of the plate 15 and the lower side of the adjacent portion of the top wall 1.

This bafile plate 15 has an angularity with respect to the electrophotographic image plate 11, when the latter is positioned against the frame material 3, ranging from slightly less than to about 45. The plate 15 may be made of the same material as are the other walls of the a device and its height should be suflicien t to confine a pile of the developing powder 16 behind it, between the plate 15 and the adjacent end wall 7, which is suflicient to eflect adequate development of the latent electrophotographic image when passed twiceover'the image plate; I"

In operation, starting with the developing apparatus in the position shown in Figs, 1 and 4A, andfwith' the powder 16 located as'illustr'ated, and, of course, with the electrophotographic image plate'in position, the developing apparatus is rotated, either manually' or by a suitable motor drive, through one full revolution in a counterclockwise direction when looking at the drawing, as shown in Figs. 43 through 4H, inclusive. In' other words, the rotation shouldbe such that the end of the device carrying the bafiie plate 15 should go upwardly or lift at the start of the rotation. t

With continued rotation the plate'15 holds the developing powder '16 in place as the mouth portion 9 raises, as in Figs. 4B and 4C. In other words, during this phase of the rotation the plate '15 functions as" a bottom' wall for the container having the mouth 9. The plate 15 defines a pocket or container which extends inwardly "towards the container having the mouth'10 and,therefore, stores or holds the powder 16 until the image side s of the plate 11 is facing upwardly. As the device rotates about the axis established by the bearings further through angles causing the baflie plate or container or pocket bottom wall 15 to attain a declining'pdsition, as in Fig. 4D, the powder 16 begins to flow over thetop of the plate 15 and showers downwardly over" the image side'of the plate 11 to efiect the. first developing pass. The powder continues downwardly throughthe mouth and collects in the container having the mouth portion 10. It is to be noted that both mouth portions interface so that each can catch the powder from the other. a

Further rotation, as in Fig. 4E, bringsthe container having the mouth 10 to an uppermost position, in Fig. 4F, so that'the powder leaves that pocket or container and again showers downwardly over 'the image side of the plate' ll so as to -collectin the other pocket, as in Fig. 4G. The plate provides guidance forthe powder if this is needed Continued rotation, as in Fig. 4H, then bringsthedevice back to its horizontal position with the powder 16-againcollected behind the bafiie 15 It can beappreciated that essentially the devi'ce comprises a frame forpositioning the plate, aineans for pivotally mounting'this frame,.the containers for the 7 developing powder at the opposite ends of the frame, and the interfacing mouth portions for the containers, the new double-pass result being obtained by the arrangement of the baffle plate 15 which in effect causes one of the containers to extend inwardly towards the other.; The angularity of the plate 15 must, of course, provide this inwardly extending pocket with a bottom that gravitar tionally restrains the flow of the developing material while the 'frame rotates through .the .angles causing the plate 11 to face downwardly, and gravitationally causing the material or powder to flow while the frame rotates through the'angles causing the plate 11 to face upwardly at a decline from the mouth opening 9.

With this new device the desired two passes are'obtained by a single continuous rotation of the through each complete revolution.

I claim:

' An apparatus for developing electrophotographic plates comprising a rectangular, box-likeatray having a bottom device with side walls and end walls integrally connected thereto to provide adeveloping 'material container coverwportion-s connected between each end wall and adjacent portions of the side walls whereby to form covered sec-' tions of the tray 'ateach end thereof and an open portion:

therebetween 'to accommodate an, electrophotographic plate, the upper surfaces of. said cover portions and side and end walls beingsubstantially coplanar to form a hearing surface for supporting an electrophotographic"plate, clamping means mounted on-the" tray for clamping an electrophotographic plate over theiopen portion thereof, means'for supporting the tray 'for rotation about an axis intermediate its ends, and'a' substantially rectangular 'baflie formed withinonebf the covered sections of the tray, said baflle being inclinediupwardly from the bottom of the tray in the direction of theadjacent end wall and having its bottom' and "sidehedges integrally connected respectively with the bottom and side walls of the tray. and havingits top 'edge in spaced relation to theinner.

face of the adjacentcover portion. a v i References Citd-ii the file of this patent UNITED STATES; i PATENTS 1,648,504 Offenbacher; 2,393,615 Davidson Jan.29, 1946 2,550,724 7 Sahel et al. May 1, 1951 2,550,738 Wallrup Mayl, 1951 2,635,046 

